As a conventional rotation operation device, a device described in Patent Literature 1 is known, for example. A rotation operation device of Patent Literature 1 has been applied to a vehicle heater control device. A cylindrical holder is fixed to an insulating substrate, a cylindrical rotor is provided on an outer peripheral section of the holder, and further, a rotary knob is provided on the outer peripheral section of the rotor. The rotary knob is fixed to the rotor. The rotary knob and the rotor are rotatable with respect to the holder, and form a rotation operation section.
A region corresponding to the inside of the cylinder of the holder on the insulating substrate is provided with a plurality of (ten) fixed electrodes arrayed in a circumferential direction. Further, a flange section is formed at the end of the rotor on the opposite side to the insulating substrate, and a region of this flange section which is opposite to the fixed electrode is provided with a plurality of (four) movable electrodes arrayed in the circumferential direction. The surfaces of the rotor and the rotary knob are plated, and when a finger of an operator touches the rotary knob, the finger and the movable electrode come into an electrically connected state via the plating.
When the operator rotates the rotation operation section, the movable electrode passes through the plurality of fixed electrodes. At this time, the fixed electrode closest to the movable electrode comes into the electrically connected state, and a detection circuit detects the electrically connected states of the plurality of fixed electrodes. Then, from results of the above detection, a control section determines a rotation quantity and a rotation direction (clockwise or counterclockwise) of the rotation operation section, and actuates a control mechanism for controlling a temperature in the vehicle, to change a preset temperature.
However, in the rotation input device of Patent Literature 1 above, for grasping the rotation quantity and the rotation direction of the rotation operation section, the fixed electrodes are provided on the insulating substrate, and the movable electrodes are further provided in the rotation operation section, thus requiring a large number of electrodes. Then, the rotation operation section is required to have spaces for providing the movable electrodes. Further, with the movable electrodes provided in the rotation operation section, the surface of the rotation operation section (rotor and rotary knob) is plated so that the finger of the operator and the movable electrode come into electrically contact, which generally makes the cost high.